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The present invention relates to devices for leveling ladders, and more particularly to the use of wedge shaped members for leveling ladders.
A conventional extension ladder consists of a pair of lengthwise support legs, or stiles, that are joined together in a generally parallel relationship by a plurality of rungs. During use, an extension ladder is leaned against an external object, such as a wall or the side of a roof, for support. A step ladder is similar to an extension ladder, but it is provided with a second pair of support legs. The second pair of support legs make the ladder self-standing, such that it does not have to be leaned against an external object for support. During use, the rungs of a ladder are preferably kept in a horizontal orientation so as to provide secure and consistent footing for the user of the ladder and also keep the ladder vertically oriented. When a ladder is set up on an unlevel or uneven surface, such as a slopping hill, an inclined walkway, or bumpy ground, the ladder leans toward the downward slope, which typically results in a dangerous condition, given that the weight on the ladder is not centered directly over the base, i.e., centrally of the two legs. This non-centered placement generates a lateral force which tends to cause the ladder to rotate in that direction, leading potentially to a fall.
A ladder can be maintained in a substantially vertical orientation on a sloped surface by placing an object under the vertical legs of the ladder so as to counter the slope of the surface. Commonly available objects, such as boards, bricks and the like, are conventionally used for this purpose. However, because these items are not specifically designed for leveling a ladder, they are often difficult to use effectively. For example, it may be difficult to find an object of the required height for leveling the ladder on a particular slope. The use of boards, bricks and the like to level ladders may also lead to dangerous situations. For example, a ladder may slip off of a board or a brick may crumble during use, causing the ladder to fall.
In addition to common household items, various efforts have been made to design leveling devices that are specifically configured for leveling a ladder. See e.g. U.S. Pat. No. 5,339,921 (Faupel); U.S. Pat. No. 5,263,551 (Andersen); U.S. Pat. No. 5,139,109 (Clarke); U.S. Pat. No. 4,699,247 (Clarke).
The use of wedge shaped members to level ladders is known in the art. See e.g U.S. Patent 4,304,318 (Webb); U.S. Pat. No. 3,993,275(Lucas). For purposes of leveling ladders, wedges are superior to flat objects such as boards and bricks. The triangular profile of a wedge allows the wedge to be inserted under a support leg of a ladder until the leg has been raised to a desired height. This feature allows the rungs of the ladder to be leveled with precision, preventing accidents. Additionally, one wedge can be used to level a ladder along various angles of slope simply by using higher or lower regions of the wedge.
One drawback of wedges is that they have a sloped surface, which can allow a ladder to slip down the wedge, resulting in a dangerous condition. Additionally, the use of a sloped upper surface allows the force transmitted through the leg of the ladder to be applied in a partially lateral direction, which may cause the bottom surface of the wedge to slide relative to the support surface, resulting in a dangerous condition.
U.S. Pat. No. 6,164,608 (Schiel, Jr.) discloses a ladder leveling chock system that consists of a pair of wedge shaped members. Each block has top and bottom faces, an end face, and a pair of side faces. The top and bottom faces converge together at an end vertex extending between the side faces and opposite the end face. The bottom face has a resiliently deformable surface. The top face is designed for resting a lower end of a rail of a ladder thereon, and has a resiliently deformable gripping strip coupled thereto for frictionally enhancing contact between the top face and the lower end of the upright a ladder. The chocks are used to provide a stable and generally horizontal surface for resting a ladder on sloped resting surfaces. The lower end of one of the support legs of a ladder is rested on the gripping strip of the top face of the first leveling chock, while the lower end of the other leg of the ladder is rested on the gripping strip of the top face of the second leveling chock.
Schiel discloses the use of a generally rectangular depression extending between the end vertex and the end face of the top surface. The depression has side walls that preferably lie in planes substantially parallel to the side faces. A generally resiliently deformable gripping strip substantially occupies the space defined by the depression. The gripping strip has a plurality of substantially parallel gripping ridges extending between the end face and the end vertex substantially parallel to the side faces. The resiliently deformable surface of the bottom face has a plurality of substantially parallel gripping ridges extending between the side faces substantially parallel to the end face. The depression and the gripping strip are preferably centered on the top face between the side faces and occupy an area between about one quarter and about three quarters of the total area of the top face in order to center the lower end of the rail on the top face for optimizing the stability of the lower end of the rail on the block. Ideally, the depression and the gripping strip occupy about one-half of the total area of the top face. Schiel also discloses a carrying cavity for receiving fingers of a user therein to aid in carrying of the block.
U.S. Pat. No. 3,993,275 (Lucas) discloses a ladder lifting and leveling device that includes both a series of steps and an inclined plane that are part of a unitary body and are separated by a brace or ridge. Lucas discloses providing a brace or ridge on an outer edge of the inclined plane to prevent slippage of a ladder.
There is a need for a device for level ladders having the following characteristics and advantages over the prior art.
It is an objective of the invention to provide a device for leveling an OSHA-approved ladder on non-level or uneven surfaces that is easy to use, and that includes safety features for securing a ladder in place on the device and for enhancing the overall stability of the ladder. An OSHA-approved ladder is one which has pivoted feet on the bottom of the ladder side rails, such that on placement of the ladder on a surface, the feet rotate so as to be flat against the surface upon which the ladder is set, assuring as much of a secure placement as the local surface allows.
The device includes a wedge-shaped support member having a lengthwise dimension, a planar top surface, and a planar bottom surface. The top surface of the support member tapers downward from an elevated rear end to a narrow front vertex to thereby form an acute angle between the top surface and the bottom surface. A rear rail member and a pair of opposing side rail members provide a barrier for retaining the end of a ladder on the top surface. To further retain a ladder on the top surface, the top surface has a slip resistant coating.
To prevent the device from sliding on a support surface, the bottom surface of the support member has a slip resistant tread. The tread has a plurality of ribs extending downward from the bottom surface of the support member. The ribs are oriented transversely to the lengthwise dimension of the support member, such that when the bottom surface of the support member rests on the support surface, the ribs tend to prevent the support member from sliding relative to the support surface. To prevent sliding on hard surfaces such as brick or concrete, the rubber grip tread preferably consists of a hard, substantially nonresilient rubber having a durometer greater than about 45 Shore A. The ribs are preferably linear and oriented perpendicular to the lengthwise dimension of the support member. In a preferred embodiment, the ribs are between about {fraction (1/16)} to about {fraction (1/18)} inch in height and are spaced about xe2x85x9 inch to about {fraction (3/16)} inch apart.
To prevent the device from sliding on soft surfaces such as grass or dirt, the device is additionally provided with a pair of retaining member bores adjacent the elevated rear end, along with a pair of retaining members sized to fit the retaining member bores. The retaining member bores pass through the top surface and the bottom surface of the support member. The retaining members have an enlarged head portion and an elongated spike portion extending from the head portion. The spike portion is sized and configured to extend entirely through the retaining member bores, such that a lower end of the spike may be selectively extended through the retaining member bore and into the support surface to thereby anchor the support member relative to the support surface.
To further enhance the safety properties provided by the retaining members, the retaining bores are angled downward toward the rear end of the support member, preferably at an angle between about 8 and about 12 degrees relative to vertical.
To prevent the retaining members from being lost when not in use, a pair of retaining member storage bores are preferably formed in the support member for storing the retaining members.
To assist a user in lifting the retaining members from the support surface, a finger hold is preferably formed in the elevated rear end of the support member for use in lifting the device from the support surface.
To assist in storing and transporting the device, the support member is preferably provided with a ladder hanger bore. The ladder holder bore is sized and configured to allow the device to be stored on the rung of a ladder.
To insure that the device is used in a proper manner when leveling a ladder, directional indicia are preferably imprinted on the support member. The indicia indicate which direction the support member is to be inserted under the ladder.
The foregoing and other objects, features, aspects and advantages of the invention will become more apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.